Sodium caseinate, interaction with

Figure 3.6 Effect of Ca2+ content on predicted values of osmotic pressure (H, , left axis) of caseinate nanoparticles in emulsion continuous phase and the free energy of the depletion interaction (AGdep, , right axis) between a pair of emulsion droplets (

Semenova, M.G., Belyakova, L.E., Polikarpov, Yu.N., Stankovic, I., Antipova, A.S., Anokhina, M.S. (2007). Analysis of light scattering data on the sodium caseinate assembly as a response to the interactions with likely charged anionic surfactant. Food Hydrocolloids, 21, 704-715. 

In the case of the rather porous and flexible structure of sodium caseinate nanoparticles, the data show that the interaction with surfactants causes a tendency towards the shrinkage of the aggregates, most likely due to the enhanced cross-linking in their interior as a result of the protein-surfactant interaction. This appears most pronounced for the case of the anionic surfactants (CITREM and SSL) interacting with the sodium caseinate nanoparticles. Consistent with this same line of interpretation, a surfactant-induced contraction of gelatin molecules of almost 30% has been demonstrated as a result of interaction with the anionic surfactant a-olefin sulfonate (Abed and Bohidar, 2004). 

It is pertinent to note here the observed increase in the value of the structure-sensitive parameter p from 1 to 2. This implies that the architecture of the sodium caseinate aggregates, as modified by interaction with the surfactant, becomes generally more open, despite the inferred collapse of their constituent protein nanoparticles. In contrast, a shell-like aggregation structure can be inferred for the self-assembly of sodium caseinate as a result of its interaction with the non-ionic surfactant PGE (this surfactant is based on a mixture of the esters of stearic and palmitic acids in chemical combination with polyglycerol (Krog, 1997)). 

Figure 6.8 Sketch of proposed molecular mechanism of protein-surfactant interaction for CITREM + sodium caseinate (0.5 % w/v in aqueous medium (pH = 7.2, ionic strength = 0.05 M) at 293 K. Picture (I) shows the water molecules bound with polar groups of the protein and surfactant, as w ell as w ater molecules structured as a result of hydrophobic hydration around the hydrocarbon chain of the surfactant. (For clarity, the free w ater molecules are not shown.) Picture (H) demonstrates the release of bound and structured water molecules resulting Rom the predominantly hydrophobic interactions between protein and surfactant. Reproduced Rom Semenova et al. (2006) with permission.

Table 6.2 Schematic representation of nanoscale structure and experimental data relating to self-assembly of sodium caseinate induced by interactions of the protein (1.0 % w/v) with micelles of food-grade surfactants (CITREM and SSL) in an aqueous medium (pH = 5.5, ionic strength = 0.05 M, 293 K) above the surfactant cmc. 

Table 6.3 Effect of protein self-assembly, induced by interaction with lecithin, on the stability of foams stabilized by complexes of sodium caseinate (1 % w/v) with soy phospholipids Lipoid S-21 (1(T5 M) (Istarova et al., 2005 Semenova, 2007). Values of Mw and A 2 are presented for the protein with and without surfactant at three pH values. Also shown are photographs of foams recorded 9 minutes following foam preparation. In each of the images the volume of the glass vessel containing die foam is 10 ml. 

G. Doxastakis and P. Serman, The interaction of sodium caseinate with monglyceride and diglyceride at the oil-water... 

Some food proteins are rich in phosphoric acid residues. The acid may either form ester bonds with Ser residues, as in caseins and egg proteins, or stabilize the native conformation of protein micelles by electrostatic interactions with negatively charged groups and calcium ions, as in caseins. In soy proteins Ser and Thr residues can be esterihed and Lys amidated with cyclic sodium trimetaphosphate at pH 11.5 and 35°C (Sung et al., 1983) ... 

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